Squats.
What is the proper way to do one? Most of the stuff I have read says to go past parallel (butt goes past knees). Here is the a video that I used for reference.
However my gf, who has taken some fitness type classes in university, disagrees that I should be going past parallel and I am risking my knee health in doing so.
Also to note I have been going past parallel and my right knee audibly clicks sometimes. Doesn't hurt or anything, just makes a noise.